(A) the principle of determining the mining plan
Theoretically speaking, the design of mining scheme should consider the factors such as regional economic development, industrial structure adjustment and the improvement index of people's living standards, and need various information from multiple departments. Due to the limited data, the following principles are mainly considered in the design of this mining scheme.
1) First consider the rationality of the existing mining scheme, because the current mining situation reflects the needs of regional economy and people's life to a certain extent and follows the laws of local economic development.
2) The proposed mining scheme is operable and should be combined with the actual situation.
3) It plays a guiding role in the development and utilization of local groundwater resources and environmental protection.
4) Fully consider the government's development plan in the next five years, ten years or longer, and provide scientific basis for government decision-making.
(2) Determination and simulation of mining scheme
1. The forecast is 20 10 when the current output is maintained in 2004.
The groundwater level dynamics in 20 10 years are simulated and predicted by using the established groundwater numerical model of each basin, so as to maintain the groundwater exploitation model of each basin in 2004. The initial water level shall be based on the unified water level measured in June 5438 +20041October, counting from June 5438+10/October 25th.
2. Predict the change of groundwater flow field by 20 10, with the output increasing by 3% or 5%.
The principle is that the exploitation amount should be reduced where the falling funnel has appeared in the groundwater flow field, and the exploitation amount should be appropriately increased where the falling funnel has not appeared, with an average annual increase of 0.5%.
3. According to the geological environment problems that may be caused by groundwater exploitation at present, adjust the groundwater exploitation scheme in each basin and predict the adjustment scheme.
Its principle is to determine the adjustment measures of groundwater exploitation scheme according to the special environmental geological problems caused by unreasonable exploitation of groundwater in each basin, and to simulate, predict and evaluate the adjusted exploitation scheme. On this basis, reasonable mining suggestions are put forward.
Second, the optimization and comparison of different mining schemes in each basin.
(1) Simulation and prediction of current mining scheme
1. Taiyuan basin
Using the numerical model of groundwater flow in Taiyuan basin, the groundwater head dynamics under the current mining conditions are simulated and predicted. The initial condition is the current groundwater head distribution, and the boundary conditions, model parameters and various source and sink items are all parameters identified by the model. Figures 5-48 and 5-49 are partial simulation and prediction results. It can be seen that the shallow groundwater level and the middle-deep groundwater level are decreasing year by year to varying degrees, especially the middle-deep groundwater level.
2. Datong Basin
At present, the funnel in Datong City continues to expand, and the water level in the center of the funnel continues to drop, which is about 1.6m per year from 2000 to 20 10. By 20 10, the water level in the center of the funnel dropped to about 985m in June of 1 year. In non-key mining areas, the change of deep groundwater level is not obvious. The simulation results are shown in Figure 5-50.
The central water level of deep funnel in Shuozhou key mining area is decreasing at the rate of 1. 1m every year. When it reaches 20 10, it will drop to about1090 m. In non-key mining areas, the deep groundwater level in Shuoxian and Yin Shan also tends to decrease slowly.
3. Xinzhou Basin
Scheme 1. Maintain the existing mining quantity, mining mode and distribution unchanged, and predict the changes of groundwater quantity and water level in the study area after 5 years.
A) Take the monthly average rainfall in recent five years (1998 ~ 2002) and predict the change of groundwater level in the basin after five years;
B) The monthly average rainfall of low water of nearly 10a is used to predict the change of groundwater quantity and water level in the basin after five years.
For the convenience of model calculation and input, the actual input rainfall in scheme b) is the ratio of the average annual rainfall in dry season to the average annual rainfall in normal season (take 0.827), which is obtained by multiplying the rainfall in scheme a).
Figure 5-48 20 10 to 1, shallow isobar of Taiyuan basin with constant output.
Figure 5-49 isobar (m) 5-49 20 10/0 to 1 Taiyuan middle-deep layer, with the same exploitation amount.
Scheme 1 simulation and its results.
Scheme1a. Keep the existing mining status unchanged and continue mining to 20 10 and 12. Simulation results: Plane isobar figure 5-5 1 and figure 5-52.
Scheme1b. Compared with the scheme 1a, the rainfall is nearly 10a, and the change of groundwater quantity and water level in the study area after 5 years is predicted.
Result analysis. Combining the isobar diagram and water level change curve (Figure 5-53 and Figure 5-54), it can be seen that the groundwater level in Xinzhou Basin is declining, and there are two modes of water level decline: one is the main urban area, that is, the main industrial and mining area. Due to a large number of centralized mining, the water level in these areas has dropped significantly, and there are different degrees of groundwater drop funnels, which is a serious problem; The other is in other areas except urban areas. Although the groundwater level has declined, the trend is relatively gentle and stable.
4.linfen basin
Using the numerical model of groundwater flow in Linfen basin, the groundwater head dynamics under the current mining conditions are simulated and predicted. The initial condition is the current groundwater head distribution, and the boundary conditions, model parameters and various source and sink items are all parameters identified by the model. Figures 5-55 to 5-58 are partial simulation and prediction results. It can be seen that the shallow groundwater level and the middle-deep groundwater level are decreasing year by year to varying degrees, especially the middle-deep groundwater level. By 20 10, large-scale landing funnels appeared in huozhou city, houma city, Linfen and Xiangfen.
Fig. 5-50 Variation of shallow water level isoline (m) in Datong Basin 5-50 20 10/0.
Fig. 5-5 1 isoline map of shallow groundwater prediction in Xinzhou basin (M)20 10 February.
Fig. 5-5220 10 and 12 isograms of groundwater in Xinzhou basin (m).
5. Yuncheng Basin
Keep the current mining state, and predict the change of isoline of shallow and middle-deep water level at the beginning of 201/kloc-0. See Figure 5-59.
The simulation results show that the groundwater level drops and some shallow areas are drained. The middle and deep water levels in some areas have also declined.
Figure 5-53 Isogram Prediction of Shallow Groundwater in Xinzhou Basin 20 10 and 12 (m)
Fig. 5-54 isoline map of mid-deep groundwater prediction in Xinzhou basin in February 5-54 20 10/0 (m).
Fig. 5-5520 10 Isohydrograph (m) of Linfen Basin 1 layer in May.
Figure 5-56 Isohydrograph (M) of Layer 5 in Linfen Basin in May 2005
6. Changzhi Basin
The changes of groundwater quantity and water level in Changzhi basin after five years are predicted under the condition of maintaining the current mining quantity and mining mode and rainfall approaching 10a.
Figure 5-60 is the calculation result of groundwater isobar in Changzhi Basin. The solid line in the figure represents the unified measured water level in June 5438+ 10, 2005, and the dashed line represents the simulated water level in February 20 10. It can be seen that in the current mining state, the industrial mining water level near the water source in Tunliu Xidian area has dropped rapidly, from 2005 to 20 10, with a speed of 4m every year.
Figure 5-5720 10 September Linfen Basin 1 Layer Isohydrograph (m).
Fig. 5-58 Isohydrograph (m) of 5 layers in Linfen Basin in 5-58 20 10/0.
Figure 5-59 20 1 1(δ: dry unit) Isogram of Shallow Water Level in Yuncheng Basin (M)
(2) Simulation and prediction of the slow growth of production.
1. Taiyuan basin
The economy of small and medium-sized cities in Shanxi Province is still dominated by extensive development. If the national average economic growth rate is 6%, and the water consumption is also increasing 1%, we predict the change of groundwater level in key mining areas in Taiyuan Basin 1 1 counties and cities (Taiyuan City is not within the forecast range).
The isoline of shallow water level 740m and 750m changes obviously, indicating that the non-key mining areas in the plain will also be obviously affected. This will lead to a significant drop in the groundwater level in agricultural production areas, which will cause serious harm to local agricultural production. The expansion of 720m equivalent closed area in the middle and deep layer is very obvious, which indicates that a larger area of confined aquifer will be drained. Therefore, this mining method must be banned.
Fig. 5-60 20 10, 12 Comparison of shallow simulated isoline in Changzhi Basin with measured isoline in 2005 and 10.
Figure 5-6 1 20 10 Prediction of Shallow Water Level Change in Taiyuan Basin in February (m)
2. Datong Basin
According to the growth rate of local economy and population, the water consumption has increased year by year, and the mining volume has increased by 3% in five years, that is, the average mining volume has increased by 0.6% every year. When the rainfall is still the average rainfall for many years, the change of groundwater quantity and water level in the study area after 5 years is predicted.
As can be seen from Figure 5-62, the isoline of deep water level in most areas has not changed much, maintaining a steady downward trend, but the funnel area has obviously expanded and deepened, and the change is more intense, so measures must be taken.
The funnel area keeps a rapid downward trend, and the areas with less mining are also declining, but the decline is less. Therefore, it is impossible to continue mining in this way, and the mining scheme must be adjusted, otherwise the exploitable groundwater resources will decrease year by year and the groundwater level in the funnel area will drop rapidly.
Fig. 5-62 Prediction of water level change in Datong Basin in 5-62 20 10/0.
3. Xinzhou Basin
Option 2. According to the local economy, population growth and water consumption increasing year by year, the changes of groundwater quantity and water level in the study area after 5 years are predicted.
A) Take the monthly average rainfall in recent five years (1998 ~ 2002) and predict the changes of groundwater quantity and water level in the basin after five years;
B) The monthly average rainfall of low water of nearly 10a is used to predict the change of groundwater quantity and water level in the basin after five years.
Scheme 2a. When the average rainfall is nearly 5 years (1998 ~ 2002), predict the changes of groundwater quantity and water level in the study area after 5 years;
According to the economic development and population growth of Xinzhou basin, the exploitation amount is increasing year by year, which is based on the groundwater flow simulation of 20 10 ~ 12.
Mainly based on the comparative analysis of the economic growth rate of counties and cities in Xinzhou Basin and the exploitation amount of Xinzhou Basin 199 1 2004, the annual increase of groundwater exploitation is shown in Table 5-35.
Calculated by the annual increase of mining volume, the annual growth rate of industrial mining volume is 1.56%, while that of agricultural mining volume is 0.99%. Used to predict the output after 2005, and then used for simulation calculation.
Table 5-35 Annual Increase of Groundwater Exploitation (104 m3)
Fig. 5-63 Prediction of shallow (left) and middle-deep (right) groundwater isoline (m) in February 5-63 20 10/0.
Option 2b. Compared with Scheme 2a, the rainfall is nearly 10a, and the changes of groundwater quantity and water level in the study area after 5 years are predicted.
Analysis of simulation results: compared with the scheme 1, the scheme increases the exploitation amount in the same proportion, and has little influence on the overall isobar shape of the basin, but the groundwater decline rate in the main city increases, with the water level decline rate of Yuanping County being 4.2m/a, Xinfu City being 3.2m/a and Dingxiang City being-2.68m/a; The water level in non-mining areas has basically not changed or has not changed obviously. Due to the increase of output, the fluctuation range of water level fluctuation unit in scheme 1 has a slightly decreasing trend, but the change is not significant. Generally speaking, there is not much difference between Scheme 2 and Scheme 1.
4.linfen basin
The principle is that the exploitation amount should be reduced where the falling funnel has appeared in the groundwater flow field, and the exploitation amount should be appropriately increased where the falling funnel has not appeared, with an average annual increase of 0.5%.
After increasing mining, in May of 20 10, a bucket fell in the southwest of Linfen 1 floor, and the funnel expanded year by year. The water levels in Jishan County and the northeast of houma city are also decreasing year by year. In May 2004, a descending funnel appeared in the south of Linfen, the fifth floor, and the funnel expanded westward year by year. On May 9, 2004, a descending funnel appeared in the southwest of huozhou city, the south of Linfen, Xinjiang County and the southwest of houma city. By May of 20 10, the groundwater level in the north of Linfen decreased, the funnel in the southwest expanded year by year, and the water level in Jishan County decreased. In a word, the shallow and middle-deep groundwater levels in the southwest of Linfen, Jishan, Xinjiang and houma city are decreasing year by year, so the exploitation amount in this area should be controlled to prevent funnel-shaped drainage. See Figure 5-64, Figure 5-65, Figure 5-66 and Figure 5-67.
Figure 5-64 Isohydrograph of Linfen Basin 1 Layer in May 2004 (M)
Fig. 5-6520 10 may Linfen basin 1 layer isobar (m).
Figure 5-66 Isohydrograph (M) of Layer 5 in Linfen Basin in May 2004
Fig. 5-67 Isohydrograph (M) of the 5th layer in Linfen Basin in 5-67 20 10/0.
5. Yuncheng Basin
By 20 1 1, the exploitation along the Yellow River and the salt lake area will increase by 5%, and the water level change is predicted (see Figure 5-68).
The groundwater level drops rapidly and the area of shallow drainage area increases (the triangle symbol area in the figure is drainage area), so adjustment measures must be taken.
Figure 5-68 Shallow 20 1 1 Isohydrograph (m) in Yuncheng Basin Scheme II
6. Changzhi Basin
According to the growth rate of local economy and population, the water consumption has increased year by year, and the mining volume has increased by 2% in five years, that is, the average mining volume has increased by 0.4% every year. When the rainfall is still close to 10a, the changes of groundwater quantity and water level in the study area after 5 years are predicted.
Figure 5-69 shows the contour map of shallow groundwater level with increased mining forecast in June 20 10 (the solid line shows the unified measured water level in June 2005+00, and the dotted line shows the simulated calculated water level with increased mining forecast in February 20 10). Comparing the flow field diagram obtained by the two schemes with the water level variation diagram of the simulation unit, it can be known that the five-year rainfall is still close to 10a when the mining output increases by 2%. Compared with the current mining conditions, the falling funnel near Xidian water source in Tunliu is further expanded. The model reflects that the funnel occupying Xidian water source has expanded by 0.02km2, and the water level of simulation unit has not changed much, while the water level of simulation unit in Changzi and Changzhi areas has slightly decreased.
Fig. 5-69 Comparison between the simulated isoline of Changzhi Basin in June 20 10 and the measured isoline of June 2005 +00 in Scheme 2.
(3) Simulation and prediction of preliminary adjustment of mining scheme
1. Taiyuan basin
Adjustment and prediction of groundwater exploitation in Taiyuan basin after the Yellow River diversion into Shanxi Province
According to the implementation progress of the Yellow River Diversion Project, the average daily water supply in Taiyuan City was 2 1× 104 t from October 2004 to October 2005, and1t from June 2005 to June 2006. With the arrival of Yellow River water, Taiyuan municipal government has implemented pressure mining measures. By February, 2005, 24 self-prepared wells 124 were closed in the city, and the groundwater exploitation was reduced by 23.4×104 t/d. ..
The prediction simulation of the following design mainly predicts the distribution of mining quantity in Taiyuan City.
In the GMS model, the measures to suppress production are mainly taken in Nanwu City and xiaodian district City of Taiyuan City (some mining wells are closed). The production of Taiyuan started from 65438+ in1October, 2004, and the simulation time was from 1990 1 to 20 10.
Analysis of groundwater level prediction results;
1) The central head of deep funnel in Nanwu City, Taiyuan City has increased by about 60m from 2005 to 20 10. The medium-deep funnel in the store will rise by 35m when it reaches 20 10, and it can almost recover to the head of 1990.
2) From the head change curve of the funnel center simulation unit, the water level rises rapidly at the beginning of pressure mining, and then gradually slows down.
See Figure 5-70 for the isograms of simulated water level in the middle and deep layers.
Figure 5-70 20 10 and 10 Prediction of water level change in middle and deep layers (m)
2. Datong Basin
According to the preliminary water supply plan, in 20 10, the north main line of YRDP will supply water to Datong and Heping Shuo 1.6× 108 m3, 4.42× 108 m3 in 2020 and 5.6×65438+ in 2030.
The following is a simulation calculation based on water shortage when the water supply guarantee rate is 95%. We didn't consider crowding out water, but used the imported Yellow River water to replace part of groundwater exploitation, so that part of groundwater could recuperate.
The Yellow River water came in. According to this distribution plan, the range of several funnels in Datong City was slightly expanded from 2006 to 20 10, but the water level in the center of the funnel was restored. The simulation unit 63093 in the north funnel rises at a rate of about 1m per year. By 2030, the water level will return to about 980m m. The water level of the simulation unit 62873 in the northern funnel area will rise by about 15m, and will reach about 1 002m by 2030. The water level of 63754 in the south funnel simulation area will be restored to 20m, and will reach about 988m by 2030. Simulation units 63432, 63544, 6365 1 are less affected, and the change of groundwater level is not obvious.
By studying the water level changes of several simulation units, the influence of this water resources allocation mode on the groundwater level in the study area is analyzed. Through constant revision, the best scheme is obtained and applied to production practice.
Table 5-36 Supply and Demand of Water Resources in Datong Basin
Note: Of the water occupied by 1.65× 108 m3, Datong is 0.55× 108 m3 and Pingshuo is1.10×108m3.
Table 5-37 Prediction Model (108m3 A- 1) Adjustment Scheme for Water Diversion from the Yellow River
3. Xinzhou Basin
Option 3. On the basis of the second scheme, the regional adjustment of the exploitation amount is carried out in the area where the water level continues to decline, and the groundwater quantity and water level change in the study area after 5 years are predicted. The change trend of total production follows the change rate of production in scheme 2; Rainfall adopts scheme b) in the first two schemes.
In order to alleviate the problem of groundwater falling funnel, we try to disperse industrial mining points around the city and distribute the original mining wells more reasonably to slow down the rapid decline of groundwater level in the center of groundwater falling funnel.
The water level of the main mining wells in Yuanping County continues to decline at a rate of-3.67m/year.
The water level of main mining wells in Xinfu urban area is continuously decreasing at a rate of-1.88 m/a.
Because the total amount of mining remains unchanged, the amount of sources and sinks remains unchanged, and only the mining layout is changed, so the total water balance remains unchanged.
Result analysis. Because this plan only further disperses the production volume, but does not reduce the total production volume, it has little influence on the regional water level change, but it still alleviates the water level decline in the center of main production wells to some extent (Table 5-38).
4.linfen basin
On the basis of the second scheme, the regional adjustment of mining quantity is carried out in the area where the water level continues to decline, and the change of groundwater level in the study area in 20 10 is predicted. However, the total amount of mining remains unchanged; The first two schemes are used for rainfall (because the specific exploitation amount of wells is not known in advance, only the exploitation amount of counties and cities is known, but it is allocated to wells according to the exploitation amount of counties and cities; In addition, the statistics of the number of mining wells are not completely accurate, so the production volume is adjusted by region).
Fig. 5-7 1 prediction of shallow water level change in Datong basin in 20 years 10 and10.
Figure 5-72 20 10 and 12 Isograms of Shallow Groundwater in Xinzhou Basin (M).
Fig. 5-73 20 10 and 12 isograms of groundwater in Xinzhou basin (m).
Table 5-38 Comparison of water level decline trend in main mining areas under different schemes (predicted to 20 10)
Referring to the simulation results of the previous two schemes, it can be seen that the groundwater problem in Linfen Basin mainly appears in the area where urban industrial exploitation is concentrated. Due to the continuous development of the city and the continuous expansion of the urban area, in order to alleviate the problem of groundwater falling funnel, we try to disperse industrial mining points around the city and distribute the original mining wells more reasonably to slow down the rapid decline of groundwater level in the center of groundwater falling funnel.
Fig. 5-74 Comparison between simulated shallow water level and measured water level (m) of Linfen Basin Scheme 3 20 10.
The water levels in the Tuergou area in the northeast of Hongtong County, the west of Nanshou City in Yicheng County, the north of Xizhuang in houma city, the south of Xiangfen County, Duzhuang in huozhou city and the northwest of Yanjiazhuang in the southeast of huozhou city basically showed a downward trend from 2004 to 20 10. Although there is no falling funnel in some places, the water level continues to drop. In case of falling funnel, attention should be paid to it, thus causing environmental geological problems related to the water environment. Joy area in houma city should be exploited by water source, and the water level continued to decline in 2004, and it was basically stable from 2005 to 20 10. The water level in some places in Quwo and Hejin has risen.
5. Yuncheng Basin
Through the prediction and analysis of the first two schemes, it shows that there is drainage in some shallow areas, and the groundwater resources in the middle and deep layers are relatively rich; However, it is difficult to replenish the middle and deep groundwater resources, so it is recommended not to over-exploit. Therefore, this scheme is designed and studied in the low sequence area of the Yellow River, and mixed production wells are arranged to exploit shallow and middle-deep groundwater.
Scheme. There are 50 production wells in Yongji terrace, with a daily output of 7 000m3 per single well and an average pressure production of 26× 104m3 in the basin. The simulation results are shown in Figure 5-75.
Result analysis. The water level of 20 1 1 in the water source area of Yongji Yellow River terrace generally decreased by about 8m, while the water level in the internal pressure production area increased slightly.
6. Changzhi Basin
Optimization scheme 1: adjust the water source exploitation in Tunliu West Power Station.
By comparing the first two mining schemes, it can be seen that the water level of the water source located in Tunliu Xidian is decreasing at a faster speed, which is 4 m/a; Moreover, with the increase of mining volume year by year, the area of the falling funnel is further expanded, which will have a negative impact on the environment in this area.
On the basis of the second scheme, the total amount of exploitation in the water source is kept unchanged, the number of exploitation wells in the simulation unit near the water source is increased, and the water level changes near the water source with different numbers of exploitation wells are increased. The simulation results are shown in Figure 5-76 and Figure 5-77.
Fig. 5-75 Simulated Contour Line (m) of Yellow River Terrace Water Source in Yuncheng Basin
A) 1 production well is added to the adjacent unit of the simulation unit where the water source is located, and the output of the water source is equally distributed to these two wells.
B) Add 1 production well to the simulation unit where the water source is located, and distribute the output of the water source to these four wells equally.
Figure 5-76 Changzhi Basin Scheme A2065438+6543800+February 1 Layer Isohydrograph (M)
Figure 5-77 Isohydrograph (M) of Changzhi Basin Scheme B2065438+65438 at 00+02 layer
Optimization scheme 2: increase the groundwater exploitation near the river.
The main source of groundwater recharge in Changzhi Basin is atmospheric precipitation. In the area near the river, the vadose zone has good permeability and shallow water level, and the groundwater receives a lot of rainfall recharge. When there is abundant rainfall in these areas, the groundwater level will rise and the evaporation will also increase. Increasing the groundwater exploitation near the river bank can reduce the unnecessary loss of groundwater caused by evaporation.
Taking Changzhi City as an example, under the condition of keeping the total amount of agricultural domestic water exploitation in the suburbs of Changzhi City unchanged, we will increase the exploitation near the river and reduce the exploitation on the far bank. Scheme c) Allocate 60% of the total exploitation to the area near the river; Scheme d) Allocate 80% of the total exploitation to the area near the river.
Figure 5-78 and Figure 5-79 show the isoline map of shallow groundwater level predicted by adjustment scheme c) and adjustment scheme d) in February of 20 10, respectively. By comparing the flow fields of the two schemes and the water level changes of some simulation units, it can be seen that the groundwater level in scheme D) is lower than that in scheme C), but the decline is not large, while the water level in the far river bank area is slightly higher.
Figure 5-78 Changzhi Basin Adjustment Plan c) February 1 Layer Isohydrograph (M)c)20 10.
Fig. 5-79 Adjustment Scheme of Changzhi Basin d) February 1 Layer Isohydrograph (M)d)20 10.